You need to use PowerShell to do this, the process is simply disable the mailbox, enable mail-user for the same object and copy all relevant attributes. You can adapt the script they have on the O365 wiki site:

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See how one of the leading financial services organizations uses Recorded Future as part of a holistic threat intelligence program to promote security awareness and proactively and efficiently identify threats.

Is your Office 365 signature not working the way you want it to? Are signature updates taking up too much of your time? Let's run through the most common problems that an IT administrator can encounter when dealing with Office 365 email signatures.

To show how to create a transport rule in Exchange 2013. We show this process by using the Exchange Admin Center.
Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center.
Navigate to the Mail Flow >> Rules tab.: To cr…

Polish reports in Access so they look terrific. Take yourself to another level. Equations, Back Color, Alternate Back Color. Write easy VBA Code. Tighten space to use less pages. Launch report from a menu, considering criteria only when it is filled…